Such a jet pipe is disclosed in the German Patent Specification 21 50 711. In this known jet pipe the section adjacent to the suction inlet and the conical tubular portion are interconnected by means of screws. In the operation of such a jet pipe highly pressurized water is supplied to the supply piece and enters the tubular interior through outlet openings in direction of a conical envelope. By means of this effect a sand-water or soil-water mixture is aspirated at the inlet and passed through the conical water envelope. A swirling action occurs which leads to high wear of the conical tubular portion and of the region comprising the outlet openings. A replacement of worn parts leads to considerable non-productive time, in particular where two such jet pipes are connected in series.
German Patent DD 153 905 discloses a multi-stage jet pipe having a cylindrical or divergent section following a diffusor. The individual stages are interconnected by means of screws. U.S. Pat. No. 2,396,290 discloses a multi-stage jet pump having divergent or cylindrical sections following the diffusor. Individual sections of the apparatus are screwed together.